Abstract: A subscriber line interface circuit that provides regulated current to telephone subscribers in an improved manner reducing the amount of power required to operate while maintaining a constant current source. The current to the telephone subscribers flows through a switching transistor, an inductive storage element, sensing resistors and a transformer. The desired operating characteristic is obtained by cycling the switching transistor. The switching transistor is cycled on at a preset interval causing the telephone subscriber current to flow from the switching transistor. The switching transistor is cycled off in response to an increase in the telephone subscriber current as sensed by the sensing resistors thereby causing the current to flow from the inductive storage element.

Abstract: A power supply is provided with a predetermined nonlinear temperature coefficient for float charging sealed lead-acid batteries and providing power to a load. A temperature compensation network in the power supply provides the predetermined nonlinear temperature coefficient by using a linear temperature coefficient element (forward biased silicon diode) and a nonlinear temperature coefficient element (thermistor) in combination. Additionally, an over-voltage protection circuit, to disable the power supply should the output voltage exceed a predetermined value, is disclosed having a second temperature compensation network to compensate for the output voltage variation with temperature of the power supply.

Abstract: A subscriber power supply which delivers sufficient power to a subscriber terminal load despite variations in load current due to changes in the number of channels in a telephone carrier system. The power supply also has a back-up unit which operates to deliver power to the load in the event that a fault occurs in the primary supply.

Abstract: A universal station identification circuit arrangement for use with central office equipment that utilizes either differential or longitudinal detection methods is adapted to be connected to the tip party's subscriber drop in a two-party line without requiring access to or rewiring of the tip party's telephone. The circuit arrangement may be fabricated in a single unit which may include a ringer isolator together with ANI mark circuits.

Abstract: An electronic hybrid having a two-wire port adapted to be connected to a two-wire line and separate unidirectional receive and transmit ports, means for coupling signals received at said two-wire port to said transmit port, and a circuit for converting single-end signals imposed on the receive port into differential signals for application to the two-wire port.

Abstract: An equipment protector and energy saving apparatus includes transient protection as well as under voltage protection by preventing the reduced voltage from being applied to motors and other apparatuses that may be damaged because of insufficient voltage being applied thereto. Provision is incorporated to protect for momentary low voltage transients and turn-on prevention, if the line voltage should be reduced below a predetermined value. Provision is also made for correcting for a small increase in line voltage which may occur when the operating equipment is removed from the line. A timing device may be incorporated therein in order to remove the protected equipment from the line for predetermined intervals of time.

Abstract: A signal-amplifying telephone carrier repeater which is automatically self-adjusting for both cable length and cable gauge in a plural channel, frequency division multiplexed, amplitude modulated carrier system. Also disclosed herein is a subscriber power supply which delivers sufficient power to the subscriber terminal load despite variations in load current due to changes in the number of channels in the carrier system. The power supply also has a back-up unit which operates to deliver power to the load in the event that a fault occurs in the primary supply.

Abstract: An electronic hybrid for coupling a two-wire line to a four-wire line and having a two-wire port adapted to be connected to the two-wire line, separate receive and transmit ports adapted to be connected to said four-wire line, means for coupling signals received at said two-wire port to said tramsmit port, and a circuit connected to said receive and two-wire ports and including a pair of constant current sources for driving the two-wire line that is connected to said two-wire port in response to a signal imposed on said receive port.